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Adamczyk WM, Ramu V, Jackson C, Schulze G, Goldschneider KR, Kashikar-Zuck S, King CD, Coghill RC. Radiation of pain: Psychophysical evidence for a population coding mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.02.587666. [PMID: 38617343 PMCID: PMC11014521 DOI: 10.1101/2024.04.02.587666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The spread of pain across body locations remains poorly understood but may provide important insights into the encoding of sensory features of noxious stimuli by populations of neurons. In this psychophysical experiment, we hypothesized that more intense noxious stimuli would lead to spread of pain, but more intense light stimuli would not produce perceptual radiation. Fifty healthy volunteers participated in this study wherein four intensities of noxious stimuli (43, 45, 47 and 49°C) were applied to glabrous (hand) and hairy skin (forearm) skin with 5s and 10s durations. Also, four different intensities of visual stimuli displayed on the target bodily area were utilized as a control. Participants provided pain (and light) spatial extent ratings as well as pain (and light) intensity ratings. In the extent rating procedure, participants adjusted the extent of the square displayed on the screen with the extent of pain (or light) which they experienced. Pain extent ratings showed statistically significant radiation of pain indicated by 12.42× greater spatial spread of pain (pain extent) than the area of the stimulation with 49°C ( p < 0.001), in contrast to visual ratings which closely approximated the size of the stimulus (1.22×). Pain radiation was more pronounced in hairy than glabrous skin ( p < 0.05) and was more pronounced with longer stimulus duration ( p < 0.001). Pain intensity explained, on average, only 14% of the pain radiation variability. The relative independence of the pain radiation from perceived pain intensity indicates that distinct components of population coding mechanisms may be involved in the spatial representation of pain versus intensity coding.
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Rujoie A, Andersen OK, Frahm KS. Investigation of directional discrimination in the nociceptive system using temperature-controlled laser stimuli. Eur J Pain 2024. [PMID: 38440936 DOI: 10.1002/ejp.2259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 01/30/2024] [Accepted: 02/26/2024] [Indexed: 03/06/2024]
Abstract
BACKGROUND Cutaneous laser stimulation has commonly been employed to investigate the thermal properties of the nociceptive system. The aim of this study was to investigate how a temperature-controlled laser system improves the assessment of directional discrimination in the nociceptive system. METHODS In total, twenty healthy volunteers participated in this study. To determine the directional discrimination threshold (stimulation length 50% correct, expressed in mm), thermal stimuli were delivered using a diode laser and the laser beam was perpendicularly displaced across the skin to give a linear stimulation in four different directions (distal, proximal, lateral and medial) and displacement lengths (3 for lateral-medial and 5 for distal-proximal). Two temperature control modes were used in the stimulation system, open-loop and closed-loop control. The subjects had to report the perceived stimulus direction, the degree of certainty regarding the perceived direction and the intensity of the perceived stimulus (0-10 numerical rating scale, 3: pain threshold). RESULTS During closed-loop control, the orientation of stimuli was discriminated significantly more accurately than during open-loop control. During closed-loop control, the directional discrimination threshold was 31.9 and 26.1 mm for distal-proximal and lateral-medial directed stimuli, respectively. A numerical rating scale was significantly higher for the lateral/medial directions. Moreover, the variability of the discrimination threshold is reduced in the closed-loop control system. CONCLUSIONS The findings show that discrimination ability is better in the lateral-medial directions compared to the distal-proximal directions. This study indicates that using a system enabling closed-loop temperature control, allows more robust probing of the temporo-spatial mechanisms in the nociceptive system. SIGNIFICANCE This study shows that a newly developed temperature-controlled laser stimulation system enhances the possibilities to investigate the nociceptive temporo-spatial integration, as shown by a less variable directional discrimination threshold. The results also show that different orthogonal directions are discriminated differently. This new method allows a better investigation of the combined temporal and spatial mechanisms in the nociceptive system.
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Affiliation(s)
- Ahmad Rujoie
- Integrative Neuroscience Group, Center for Neuroplasticity and Pain (CNAP), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark
| | - Ole Kaeseler Andersen
- Integrative Neuroscience Group, Center for Neuroplasticity and Pain (CNAP), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark
| | - Ken Steffen Frahm
- Integrative Neuroscience Group, Center for Neuroplasticity and Pain (CNAP), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark
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Nastaj J, Skalski J, Budzisz A, Szikszay TM, Swoboda S, Kowalska W, Nowak D, Zbroja E, Kruszyna N, Jakubińska M, Grygny D, Polczyk R, Małecki A, Luedtke K, Adamczyk WM. Spatial summation of pain is associated with pain expectations: Results from a home-based paradigm. PLoS One 2024; 19:e0297067. [PMID: 38300918 PMCID: PMC10833545 DOI: 10.1371/journal.pone.0297067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Accepted: 12/23/2023] [Indexed: 02/03/2024] Open
Abstract
The purpose of this study was to reproduce the previously observed spatial summation of pain effect (SSp) using non-laboratory procedures and commercial equipment. An additional aim was to explore the association between expectations and SSp. The Cold Pressor Task (CPT) was used to induce SSp. Healthy participants (N = 68) immersed their non-dominant hands (divided into 5 segments) into cold water (CPT). Two conditions were used 1) gradual hand immersion (ascending condition) and 2) gradual hand withdrawal (descending condition). Pain intensity was measured on a Visual Analogue Scale (VAS). Psychological factors, such as the participants' expectations of pain intensity were also measured on a VAS. Results showed significant SSp (χ2(4) = 116.90, p < 0.001), reproduced with non-laboratory equipment in a home-based set-up. Furthermore, two novel findings were observed: i) there was a significant correlation between expectations and perceived pain, indicating a link between pain expectations and SSp, ii) spatial summation increased with the increase in duration exposure to the noxious stimulus (Wald χ2(8) = 80.80, p < 0.001). This study suggests that SSp is associated with pain expectations and can be formed by a mixture of excitatory and inhibitory mechanisms potentially driven by temporal characteristics of neural excitation. Moreover, this study proposes a new feasible way to induce SSp using a home-based set-up.
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Affiliation(s)
- Jakub Nastaj
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Jacek Skalski
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Aleksandra Budzisz
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Tibor M. Szikszay
- Institute of Health Sciences, Department of Physiotherapy, Pain & Exercise Research Lübeck, Universität zu Lübeck, Lübeck, Germany
| | - Sylwia Swoboda
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Weronika Kowalska
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Daria Nowak
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Edyta Zbroja
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Natalia Kruszyna
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Marta Jakubińska
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Dominika Grygny
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Romuald Polczyk
- Institute of Psychology, Jagiellonian University, Kraków, Poland
| | - Andrzej Małecki
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Kerstin Luedtke
- Institute of Health Sciences, Department of Physiotherapy, Pain & Exercise Research Lübeck, Universität zu Lübeck, Lübeck, Germany
| | - Wacław M. Adamczyk
- Laboratory of Pain Research, Institute of Physiotherapy and Health Science, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
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Boudreau SA, Jakobsen TL, Haraldsson BÞ, Clausen MB. Digital mapping of shoulder pain in patients with shoulder disorders: a reliability study. Physiother Theory Pract 2024:1-13. [PMID: 38214518 DOI: 10.1080/09593985.2023.2300753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Accepted: 12/22/2023] [Indexed: 01/13/2024]
Abstract
INTRODUCTION Digital body mapping can be used to document and quantify the area and location (distribution) of pain and discomfort and support assessment, monitoring, and treatment in clinical populations. This study determines the test-retest reliability of drawings detailing pain and pins and needles using digital body charts and their relationship to pain intensity and patient-reported shoulder function. METHODS Sixty-two participants with shoulder disorder completed pain and pins and needles drawings with test-retest interval of 30 minutes. Pain intensity in the last week and the patient-reported shoulder function questionnaires were completed. Area and radiating extent were determined using customized software. To assess relative and absolute test-retest reliability, the intraclass correlation coefficient (ICC3,1), standard error of measurement (SEM) and minimal detectable change (MDC95) were calculated. Regression analysis evaluated relation between area and radiating extent of pain and pins and needles with patient-reported function questionnaires. RESULTS Relative reliability for pain area and radiating extent was excellent (>0.90). Absolute reliability (SEM and MDC95) values for the pain area and radiating extent were 0.20%/34 pixels and 0.57%/94 pixels. Absolute reliability improves for smaller pain areas. Regression analysis revealed the area and radiation extent for both pain and pins and needles are independent constructs to the patient-reported function outcome when adjusted for pain intensity. CONCLUSIONS Digital body mapping assessing pain area and radiation extent in patients with shoulder disorders are reliable. The magnitude of absolute reliability suggests other sources of variability on repeat testing in this population. Pain area and radiation extent appear to be independent constructs.
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Affiliation(s)
- Shellie Ann Boudreau
- Center for Neuroplasticity and Pain (CNAP), SMI, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | | | - Bjarki Þór Haraldsson
- Physiotherapy Degree Programme, Department of Midwifery, Physiotherapy, Occupational Therapy and Psychomotor Therapy, Faculty of Health, University College Copenhagen, Copenhagen NV, Denmark
| | - Mikkel Bek Clausen
- Physiotherapy Degree Programme, Department of Midwifery, Physiotherapy, Occupational Therapy and Psychomotor Therapy, Faculty of Health, University College Copenhagen, Copenhagen NV, Denmark
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Paredes Sanchez J, Titmus M, Lawson-Smith H, Di Pietro F. Tactile acuity improves during acute experimental pain of the limb. Pain Rep 2023; 8:e1091. [PMID: 38225958 PMCID: PMC10789456 DOI: 10.1097/pr9.0000000000001091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 05/18/2023] [Accepted: 05/26/2023] [Indexed: 01/17/2024] Open
Abstract
Introduction Chronic pain is associated with poor tactile acuity, commonly measured with the 2-point discrimination (TPD) test. Although poor tactile acuity across chronic pain conditions is well established, less is known in acute pain. Objective Recent conflicting findings in experimentally induced neck and back pain led us to conduct a TPD investigation in experimentally induced limb pain. We hypothesised altered TPD during experimental upper limb pain, but we did not speculate on the direction of the change. Methods Thirty healthy subjects immersed their dominant hand in a circulating cold-water bath at 7°C (cold pressor test [CPT]). Two-point discrimination was measured at baseline (pre-CPT), during pain (during-CPT), and after withdrawal from the water (post-CPT) in 3 different sites: (1) the dominant forearm, (2) dominant arm and (3) contralateral forearm. Results Repeated-measures analysis of variance revealed a significant main effect of time (F(2,56) = 4.45, P = 0.02, η p 2 = 0.14) on TPD; in all 3 sites, TPD values decreased (ie, tactile acuity improved) during pain. Interestingly, the contralateral forearm followed a similar pattern to the dominant (ie, painful) forearm, and furthermore was the only site that exhibited any correlation with pain, albeit in an intriguing direction (r = 0.57, P = 0.001), ie, the greater the pain the worse the tactile acuity. Conclusion The improvements in tactile acuity during experimentally induced limb pain may reflect a protective response. The changes in the corresponding site in the contralateral limb may reflect a protective spinal cross talk. Such a response, together with the interesting relationship between tactile acuity and pain, warrant further inquiry.
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Affiliation(s)
| | - Morgan Titmus
- Curtin Medical School, Curtin University, Western Australia, Australia
| | | | - Flavia Di Pietro
- Curtin Medical School, Curtin University, Western Australia, Australia
- Curtin Health and Innovation Research Institute (CHIRI), Curtin University, Western Australia, Australia
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Adamczyk WM, Katra M, Szikszay TM, Peugh J, King CD, Luedtke K, Coghill RC. Spatial Tuning in Nociceptive Processing Is Driven by Attention. THE JOURNAL OF PAIN 2023; 24:1116-1125. [PMID: 36965648 PMCID: PMC10330125 DOI: 10.1016/j.jpain.2023.03.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 03/07/2023] [Accepted: 03/13/2023] [Indexed: 03/27/2023]
Abstract
When the source of nociception expands across a body area, the experience of pain increases due to the spatial integration of nociceptive information. This well-established effect is called spatial summation of pain (SSp) and has been the subject of multiple investigations. Here, we used cold-induced SSp to investigate the effect of attention on the spatial tuning of nociceptive processing. Forty pain-free volunteers (N = 40, 20 females) participated in this experiment. They took part in an SSp paradigm based on three hand immersions into cold water (5°C): Participants either immersed the radial segment ("a"), ulnar segment ("b") or both hand segments ("a+b") and provided overall pain ratings. In some trials based on "a+b" immersions, they were also asked to provide divided (ie, first pain in "a" then in "b"; or reversed) and directed attention ratings (ie, pain only in "a" or "b"). Results confirmed a clear SSp effect in which reported pain during immersions of "a" or "b" was less intense than pain during immersions of "a+b" (P < .001). Data also confirmed that spatial tuning was altered. SSp was abolished when participants provided two ratings in a divided fashion (P < .001). Furthermore, pain was significantly lower when attention was directed only to one segment ("a" OR "b") during "a+b" immersion (P < .001). We conclude that spatial tuning is dynamically driven by attention as reflected in abolished SSp. Directed attention was sufficient to focus spatial tuning and abolish SSp. Results support the role of cognitive processes such as attention in spatial tuning. PERSPECTIVE: This article presents experimental investigation of spatial tuning in pain and offers mechanistic insights of contiguous spatial summation of pain in healthy volunteers. Depending on how pain is evaluated in terms of attentional derivative (overall pain, directed, divided attention) the pain is reduced and spatial summation abolished.
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Affiliation(s)
- Waclaw M Adamczyk
- Pediatric Pain Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Behavioral Medicine and Clinical Psychology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, Ohio; Laboratory of Pain Research, Institute of Physiotherapy and Health Sciences, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland.
| | - Michal Katra
- Laboratory of Pain Research, Institute of Physiotherapy and Health Sciences, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland
| | - Tibor M Szikszay
- Department of Physiotherapy, Pain and Exercise Research Lübeck (P.E.R.L.), Institute of Health Sciences, Universität zu Lübeck, Lübeck, Germany
| | - James Peugh
- Division of Behavioral Medicine and Clinical Psychology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, Ohio
| | - Christopher D King
- Pediatric Pain Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Behavioral Medicine and Clinical Psychology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, Ohio
| | - Kerstin Luedtke
- Laboratory of Pain Research, Institute of Physiotherapy and Health Sciences, The Jerzy Kukuczka Academy of Physical Education, Katowice, Poland; Department of Physiotherapy, Pain and Exercise Research Lübeck (P.E.R.L.), Institute of Health Sciences, Universität zu Lübeck, Lübeck, Germany
| | - Robert C Coghill
- Pediatric Pain Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Behavioral Medicine and Clinical Psychology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, Ohio
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Rujoie A, Andersen OK, Frahm KS. A novel temperature-controlled laser system to uniformly activate cutaneous thermal receptors during movable thermal stimulation. J Neural Eng 2023; 20. [PMID: 36638531 DOI: 10.1088/1741-2552/acb2f9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 01/13/2023] [Indexed: 01/15/2023]
Abstract
Objective. Laser stimulators have been widely used in pain studies to selectively activate Aδand C nociceptors without coactivation of mechanoreceptors. Temperature-controlled laser systems have been implemented with low-temperature variations during stimulations, however, these systems purely enabled stationary stimulation. This study aimed to implement, test and validate a new laser stimulation system that controls skin temperature by continuously adjusting laser output during stimulus movement to allow accurate investigation of tempo-spatial mechanisms in the nociceptive system.Approach. For validation, laser stimuli were delivered to the right forearm of eight healthy subjects using a diode laser. The laser beam was displaced across the skin to deliver a moving thermal stimulation to the skin surface. To test the function and feasibility of the system, different stimulation parameters were investigated involving two control modes (open-loop and closed-loop), three displacement velocities (5, 10 and 12 mm s-1), two intensities (high 46 °C and low 42 °C), two stimulus lengths (20 and 100 mm) and two directions (distal and proximal).Main results. During closed-loop control, the stimulation error and variation of stimulation temperatures were significantly smaller than during open-loop control. The standard deviation of stimulation temperatures increased significantly with stimulation intensity and displacement length.Significance. This study showed that more accurate, less variable laser stimulations were delivered to the skin using closed-loop control during a movable stimulus. The more uniform skin temperature during stimuli is likely to ensure a more uniform nociceptor activation.
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Affiliation(s)
- Ahmad Rujoie
- Integrative Neuroscience group, Center for Neuroplasticity and Pain (CNAP), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark
| | - Ole Kæseler Andersen
- Integrative Neuroscience group, Center for Neuroplasticity and Pain (CNAP), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark
| | - Ken Steffen Frahm
- Integrative Neuroscience group, Center for Neuroplasticity and Pain (CNAP), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark
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Northon S, Deldar Z, Piché M. Effects of spatial attention and limb position on the cortical interaction of bilateral noxious inputs. Psychophysiology 2021; 59:e13966. [PMID: 34783035 DOI: 10.1111/psyp.13966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 09/20/2021] [Accepted: 10/26/2021] [Indexed: 11/29/2022]
Abstract
Bilateral noxious inputs interact in the brain to provide a better representation of physical threat. In the present study, we investigated the effects of spatial attention and limb position on this interaction. Painful laser stimuli were applied randomly on the right hand or on both hands, while varying spatial attention (focal or overall) and limb position (hands near or far from each other). Pain perception and laser-evoked potentials (N1, N2, P2) were compared between conditions in 27 healthy volunteers. Compared with unilateral stimulation, bilateral stimulation increased pain (p = .004), the N2 (p = .0015) and P2 (p < .001) amplitude. The effects on pain and the P2 were greater when hands were in the near compared with the far position (p < .05). The effect on pain was also greater for overall compared with focal pain rating (p = .003). In addition, the N1 amplitude was greater for bilateral stimulation when hands were in the far compared with the near position (p = .01). These results show that increased brain responses and pain for bilateral compared with unilateral noxious stimulation are modulated differentially by spatial attention and limb position. This suggests that the integration of noxious inputs occurs through partially independent pain-related processes, that it is modulated by limb position, and that it is partially independent of pain perception. We propose that this is necessary to produce coordinated, flexible and adapted defensive responses.
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Affiliation(s)
- Stéphane Northon
- Department of Anatomy, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada.,CogNAC Research Group, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada
| | - Zoha Deldar
- Department of Anatomy, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada.,CogNAC Research Group, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada
| | - Mathieu Piché
- Department of Anatomy, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada.,CogNAC Research Group, Université du Québec à Trois-Rivières, Trois-Rivières, Quebec, Canada
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Henrich MC, Frahm KS, Andersen OK. Spinal spatial integration of nociception and its functional role assessed via the nociceptive withdrawal reflex and psychophysical measures in healthy humans. Physiol Rep 2021; 8:e14648. [PMID: 33217191 PMCID: PMC7679129 DOI: 10.14814/phy2.14648] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/20/2020] [Accepted: 10/23/2020] [Indexed: 12/11/2022] Open
Abstract
Animal studies have previously shown that deep dorsal horn neurons play a role in the processing of spatial characteristics of nociceptive information in mammals. Human studies have supported the role of the spinal neurons; however, the mechanisms involved, and its significance, remain to be clarified. The aim of this study was to investigate spatial aspects of the spinal integration of concurrent nociceptive electrical stimuli in healthy humans using the Nociceptive Withdrawal Reflex (NWR) as an objective indication of spinal nociceptive processing. Fifteen healthy volunteers participated in the study. Electrical stimuli were delivered, using five electrodes located across the sole of the foot in a mediolateral disposition, as a single or double simultaneous stimuli with varying Inter-Electrode Distances (IEDs). The stimulation intensity was set at 1.5× NWR threshold (TA muscle). The size of the NWR was quantified in the 60-180 ms poststimulus window as a primary outcome measure. Psychophysical measures were secondary outcomes. Single stimulation elicited significantly smaller NWRs and perceived intensity than double stimulation (p < .01), suggesting the presence of spatial summation occurring within the spinal processing. During double stimulation, increasing the inter-electrode distance produced significantly smaller NWR sizes (p < .05) but larger pain intensity ratings (p < .05). By the NWR, spatial summation was shown to affect the nociceptive processing within the spinal cord. The inhibited motor response obtained when simultaneously stimulating the medial and lateral side of the sole of the foot suggests the presence of an inhibitory mechanism with a functional, behaviorally oriented function.
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Affiliation(s)
- Mauricio Carlos Henrich
- Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg Ø, Denmark
| | - Ken Steffen Frahm
- Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg Ø, Denmark
| | - Ole Kaeseler Andersen
- Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg Ø, Denmark
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Henrich MC, Frahm KS, Andersen OK. Tempo-spatial integration of nociceptive stimuli assessed via the nociceptive withdrawal reflex in healthy humans. J Neurophysiol 2021; 126:373-382. [PMID: 34191609 DOI: 10.1152/jn.00155.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spatial information of nociceptive stimuli applied in the skin of healthy humans is integrated in the spinal cord to determine the appropriate withdrawal reflex response. Double-simultaneous stimulus applied in different skin sites are integrated, eliciting a larger reflex response. The temporal characteristics of the stimuli also modulate the reflex, e.g., by temporal summation. The primary aim of this study was to investigate how the combined tempo-spatial aspects of two stimuli are integrated in the nociceptive system. This was investigated by delivering single- and double-simultaneous stimulation and sequential stimulation with different interstimulus intervals (ISIs ranging 30-500 ms) to the sole of the foot of 15 healthy subjects. The primary outcome measure was the size of the nociceptive withdrawal reflex (NWR) recorded from the tibialis anterior (TA) and biceps femoris (BF) muscles. Pain intensity was measured using a numerical rating scale (NRS) scale. Results showed spatial summation in both TA and BF when delivering simultaneous stimulation. Simultaneous stimulation provoked larger reflexes than sequential stimulation in TA, but not in BF. Larger ISIs elicited significantly larger reflexes in TA, whereas the opposite pattern occurred in BF. This differential modulation between proximal and distal muscles suggests the presence of spinal circuits eliciting a functional reflex response based on the specific tempo-spatial characteristics of a noxious stimulus. No modulation was observed in pain intensity ratings across ISIs. Absence of modulation in the pain intensity ratings argues for an integrative mechanism located within the spinal cord governed by a need for efficient withdrawal from a potentially harmful stimulus.NEW & NOTEWORTHY Tempo-spatial integration of electrical noxious stimuli was studied using the nociceptive withdrawal reflex and a perceived intensity. Tibialis anterior and biceps femoris muscles were differentially modulated by the temporal characteristics of the stimuli and stimulated sites. These findings suggest that spinal neurons are playing an important role in the tempo-spatial integration of nociceptive information, leading to a reflex response that is distributed across multiple spinal cord segments and governed by an efficient defensive withdrawal strategy.
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Affiliation(s)
- Mauricio Carlos Henrich
- Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Ken Steffen Frahm
- Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Ole Kæseler Andersen
- Integrative Neuroscience, Center for Neuroplasticity and Pain (CNAP), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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Nonlinear increase of pain in distance-based and area-based spatial summation. Pain 2021; 162:1771-1780. [PMID: 33449502 DOI: 10.1097/j.pain.0000000000002186] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 12/30/2020] [Indexed: 11/25/2022]
Abstract
ABSTRACT When nociceptive stimulation affects a larger body area, pain increases. This effect is called spatial summation of pain (SSp). The aim of this study was to describe SSp as a function of the size or distance of a stimulated area(s) and to test how this function is shaped by the intensity and SSp test paradigm. Thirty-one healthy volunteers participated in a within-subject experiment. Participants were exposed to area-based and distanced-based SSp. For area-based SSp, electrocutaneous noxious stimuli were applied by up to 5 electrodes (5 areas) forming a line-like pattern; for distance-based SSp, the same position and lengths of stimuli were used but only 2 electrodes were stimulated. Each paradigm was repeated using pain of low, moderate, and high intensity. It was found that the pattern of pain intensity followed a logarithmic (power) rather than a linear function. The dynamics of the pain increase were significantly different across pain intensities, with more summation occurring when pain was perceived as low. Results indicated that area-based SSp is more painful than distance-based SSp when low and moderate but not when high pain intensity is induced. Presented findings have important implications for all studies in which the spatial dimension of pain is measured. When the area or separation between nociceptive stimulation increases, pain does not increase linearly and the pattern of the pain increase is a result of the interaction between intensity and the number of nociceptive sites. A power function should be considered when predicting the size of a nociceptive source.
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Frahm KS, Gervasio S. The two-point discrimination threshold depends both on the stimulation noxiousness and modality. Exp Brain Res 2021; 239:1439-1449. [PMID: 33682043 DOI: 10.1007/s00221-021-06068-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 02/18/2021] [Indexed: 11/30/2022]
Abstract
The two-point discrimination threshold (2PDT) has been used to investigate the integration of sensory information, especially in relation to spatial acuity. The 2PDT has been investigated for both innocuous mechanical stimuli and noxious thermal stimuli; however, previous studies used different stimulation modalities to compare innocuous and noxious stimuli. This study investigated the 2PDT in 19 healthy participants, using both thermal (laser) and mechanical stimulation modalities. Within each modality, both innocuous and noxious intensities were applied. Concurrent point stimuli were applied to the right volar forearm, with separation distances of 0-120 mm, in steps of 10 mm. 0 mm corresponds to a single point. Following each stimulus, the participants indicated the number of perceived points (1 or 2) and the perceived intensity (NRS: 0: no perception, 3: pain threshold, 10: maximum pain). The order of stimulation modality, intensity and distance was randomized. The 2PDT for innocuous and noxious mechanical stimuli was 34.7 mm and 47.1 mm, respectively. For thermal stimuli, the 2PDT was 80.5 mm for innocuous stimuli and 66.9 mm for noxious stimuli. The average NRS for thermal stimuli was 1.6 for innocuous intensities and 4.0 for noxious intensities, while for mechanical stimuli, the average NRS was 0.9 for innocuous intensities and 3.6 for noxious intensities. This study showed that the 2PDT highly depends on both stimulation modality and intensity. Within each modality, noxious intensities modulates the 2PDT differently, i.e., noxious intensities lowers the 2PDT for thermal stimuli, but increases the 2PDT for mechanical stimuli.
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Affiliation(s)
- Ken Steffen Frahm
- Department of Health Science and Technology, Integrative Neuroscience group, CNAP-Center for Neuroplasticity and Pain, SMI®, Aalborg University, Fredrik Bajersvej 7D3, 9220, Aalborg, Denmark.
| | - Sabata Gervasio
- Neural Engineering and Neurophysiology Group, SMI®, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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Holbert MD, Kimble RM, Jones LV, Ahmed SH, Griffin BR. Risk factors associated with higher pain levels among pediatric burn patients: a retrospective cohort study. Reg Anesth Pain Med 2020; 46:222-227. [PMID: 33168649 PMCID: PMC7907549 DOI: 10.1136/rapm-2020-101691] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 10/09/2020] [Accepted: 10/14/2020] [Indexed: 01/26/2023]
Abstract
INTRODUCTION There is an absence of evidence regarding predictors of moderate to severe pain in children undergoing acute burn treatment. This investigation aimed to determine if relationships existed between patient and clinical characteristics, and pain at first dressing change for children with acute burn injuries. METHODS A retrospective cohort investigation was conducted using clinical data from pediatric burn patients treated at the Queensland Children's Hospital, Brisbane, Australia. Data extracted included patient and burn characteristics, first aid, and follow-up care. Observational pain scores were categorized into three groups (mild, moderate, and severe pain), and bivariate and multivariable relationships were examined using proportional odds ordinal logistic regression. Data from 2013 pediatric burns patients were extracted from the database. RESULTS Factors associated with increased odds of procedural pain included: hand burns (OR 1.7, 95% CI 1.3 to 2.1, p<0.001), foot burns (OR 1.5, 95% CI 1.1 to 2.1, p<0.01), baseline pain (OR 5.5, 95% CI 2.8 to 10.8, p<0.001), deep dermal partial-thickness injuries (OR 7.9, 95% CI 4.0 to 15.6, p<0.001), increased burn size (OR 1.1, 95% CI 1.0 to 1.2, p<0.01), four or more anatomical regions burned (OR 3.6, 95% CI 1.5 to 8.6, p<0.01), initial treatment at a non-burns center (OR 1.8, 95% CI 1.4 to 2.3, p<0.001), and time to hospital presentation (OR 0.9, 95% CI 0.8 to 0.9, p<0.001). These burn characteristics are associated with increased odds of moderate to severe procedural pain during a child's first dressings change. DISCUSSION It is recommended that patients presenting with one or more of the aforementioned factors are identified before their first dressing change, so additional pain control methods can be implemented.
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Affiliation(s)
- Maleea D Holbert
- Centre for Children's Burns and Trauma Research, Queensland Health Centre for Children's Health Research, South Brisbane, Queensland, Australia .,Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Roy M Kimble
- Centre for Children's Burns and Trauma Research, Queensland Health Centre for Children's Health Research, South Brisbane, Queensland, Australia.,Pegg Leditschke Paediatric Burns Centre, Queensland Children's Hospital, South Brisbane, Queensland, Australia
| | - Lee V Jones
- Research Methods Group, Queensland University of Technology, Kelvin Grove, Queensland, Australia.,Faculty of Health, Centre for Healthcare Transformation, Queensland University of Technology, Kelvin Grove, Queensland, Australia
| | - Samiul H Ahmed
- Faculty of Medicine, The University of Queensland, Brisbane, Queensland, Australia
| | - Bronwyn R Griffin
- Centre for Children's Burns and Trauma Research, Queensland Health Centre for Children's Health Research, South Brisbane, Queensland, Australia.,Faculty of Health, School of Nursing, Queensland University of Technology, Kelvin Grove, Queensland, Australia
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The Distributed Nociceptive System: A Framework for Understanding Pain. Trends Neurosci 2020; 43:780-794. [PMID: 32800534 DOI: 10.1016/j.tins.2020.07.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 06/30/2020] [Accepted: 07/12/2020] [Indexed: 12/31/2022]
Abstract
Chronic pain remains challenging to both diagnose and treat. These challenges, in part, arise from limited systems-level understanding of the basic mechanisms that process nociceptive information and ultimately instantiate a subjectively available experience of pain. Here, I provide a framework, the distributed nociceptive system, for understanding nociceptive mechanisms at a systems level by integrating the concepts of neural population coding with distributed processing. Within this framework, wide-spread engagement of populations of neurons produces representations of nociceptive information that are highly resilient to disruption. The distributed nociceptive system provides a foundation for understanding complex spatial aspects of chronic pain and provides an impetus for nonpharmacological cognitive and physical therapies that can effectively target the highly distributed system that gives rise to an experience of pain.
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Fardo F, Beck B, Allen M, Finnerup NB. Beyond labeled lines: A population coding account of the thermal grill illusion. Neurosci Biobehav Rev 2020; 108:472-479. [DOI: 10.1016/j.neubiorev.2019.11.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 11/21/2019] [Accepted: 11/25/2019] [Indexed: 10/25/2022]
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Fardo F, Finnerup NB, Haggard P. Organization of the Thermal Grill Illusion by Spinal Segments. Ann Neurol 2018; 84:463-472. [PMID: 30063258 PMCID: PMC6175302 DOI: 10.1002/ana.25307] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 07/23/2018] [Accepted: 07/25/2018] [Indexed: 12/31/2022]
Abstract
Objective A common symptom of neuropathy is the misperception of heat and pain from cold stimuli. Similar cold allodynic sensations can be experimentally induced using the thermal grill illusion (TGI) in humans. It is currently unclear whether this interaction between thermosensory and nociceptive signals depends on spinal or supraspinal integration mechanisms. To address this issue, we developed a noninvasive protocol to assess thermosensory integration across spinal segments. Methods We leveraged anatomical knowledge regarding dermatomes and their spinal projections to investigate potential contributions of spinal integration to the TGI. We simultaneously stimulated a pair of skin locations on the arm or lower back using 1 cold (∼20°C) and 1 warm thermode (∼40°C). The 2 thermodes were always separated by a fixed physical distance on the skin, but elicited neural activity across a varying number of spinal segments, depending on which dermatomal boundaries the 2 stimuli spanned. Results Participants consistently overestimated the actual cold temperature on the skin during combined cold and warm stimulation, confirming the TGI effect. The TGI was present when cold and warm stimuli were delivered within the same dermatome, or across dermatomes corresponding to adjacent spinal segments. In striking contrast, no TGI effect was found when cold and warm stimuli projected to nonadjacent spinal segments. Interpretation These results demonstrate that the strength of the illusion is modulated by the segmental distance between cold and warm afferents. This suggests that both temperature perception and thermal–nociceptive interactions depend upon low‐level convergence mechanisms operating within a single spinal segment and its immediate neighbors. Ann Neurol 2018;84:463–472
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Affiliation(s)
- Francesca Fardo
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom.,Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Interacting Minds Center, Aarhus University, Aarhus, Denmark
| | - Nanna Brix Finnerup
- Danish Pain Research Center, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Patrick Haggard
- Institute of Cognitive Neuroscience, University College London, London, United Kingdom
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Abstract
Objectives:
The objective of this study was to study the results of the largest prospective series to date of xiphodynia patients treated by surgical xiphoidectomy.
Summary of Background Data:
Xiphodynia is a condition of recurrent and often debilitating severe upper abdominal or sternal chest pain. A retrospective analysis was conducted of 40 patients undergoing xiphoidectomy from January 2014 to January 2017.
Methods:
Preoperative and postoperative pain scales were measured, by using a standardized Wong-Baker visual pain scale, with a reported zero as no pain and 10 as worse pain. Statistical analysis of pre- and post-operative pain scale were recorded and statistical analysis completed by using a nonparametric Mann–Whitney U. The preoperative pain scale for the patient's ranged from the level of 9 to 10 (mean: 9.9).
Results:
The postoperative pain scale was rated between zero and 2 (mean: <1). There was a significant improvement in pain rating from preoperative to postoperative with a P > 0.024. All of the sports injury patients (n = 9) were back to full activity 4 to 6 weeks after the procedure.
Conclusions:
Xiphoidectomy can be an appropriate treatment modality for intractable cases of severe xiphodynia after failure of more conservative treatments. Patients with recurrence of severe, disabling pain and disability appear to benefit the most from a surgical approach based on the results of this study.
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Abstract
Spatial summation of pain (SSP) is the increase of perceived intensity that occurs as the stimulated area increases. Spatial summation of pain is subadditive in that increasing the stimulus area produces a disproportionately small increase in the perceived intensity of pain. A possible explanation for subadditive summation may be that convergent excitatory information is modulated by lateral inhibition. To test the hypothesis that lateral inhibition may limit SSP, we delivered different patterns of noxious thermal stimuli to the abdomens of 15 subjects using a computer-controlled CO2 laser. Lines (5 mm wide) of variable lengths (4, 8 cm) were compared with 2-point stimuli delivered at the same position/separation as the length of lines. When compared with one-point control stimuli, 2-point stimulus patterns produced statistically significant SSP, while no such summation was detected during line stimulus patterns. Direct comparison of pain intensity evoked by 2-point pattern stimuli with line pattern stimuli revealed that 2-point patterns were perceived as significantly more painful, despite the fact that the 2-point pattern stimulated far smaller areas of skin. Thus, the stimulation of the skin region between the endpoints of the lines appears to produce inhibition. These findings indicate that lateral inhibition limits SSP and is an intrinsic component of nociceptive information processing. Disruption of such lateral inhibition may contribute substantially to the radiation of some types of chronic pain.
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21
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Comparison of spatial summation properties at different body sites. Scand J Pain 2017; 17:126-131. [DOI: 10.1016/j.sjpain.2017.07.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 07/03/2017] [Accepted: 07/07/2017] [Indexed: 11/17/2022]
Abstract
Abstract
Background and aims
The nociceptive system appears to have evolved a range of protective characteristics that are of great interest in understanding both acute and chronic pain. Spatial summation is one important characteristic, whereby increasing area of a stimulus, or distance between multiple stimuli, results in more intense pain—not only greater area of pain. One of the mysteries of chronic pain is why spinal pain is so prevalent relative to pain at other sites. Since pathological tissue models have failed to fully explain spinal pain, we theorized that body region specific differences in sensory processing—such as a greater propensity for spatial summation—may help to explain its vulnerability. We aimed to examine this by comparing the properties of summation at different body parts: the dorsal forearm, neck, and back.
Methods
Spatial summation of pain was investigated using noxious intra-dermal electrical stimuli in healthy pain-free adults (14 males, 6 females), and the perceived pain intensity was rated on a 0-100 pain scale. Area-based stimulation was investigated by doubling the stimulation area with the addition of a second electrode placed adjacent to the first. Distance-based summation was investigated by randomly varying the separation distance between paired noxious electrical stimuli at separations of 0,10,15, and 20 cm.
Results
This study demonstrated that the properties of area- and distance-based summation are uniform across the neck, back, and forearm in healthy adults. Spatial summation of pain was also found to be greatest at 15- and 20-cm paired separations for all body regions tested, confirming that noxious information can be integrated over an extensive anatomical area.
Conclusion
Data from this investigation refutes the thesis that spatial summation of pain may be a contributing factor for the reported difference in chronicity rates between spinal and peripheral sites. It remains, however, a potentially important mechanism by which noxious inputs from multi-level pathology might integrate and contribute to pain.
Implications
While data from this project suggest that there are no regional differences in the properties of spatial summation of noxious stimuli, regional differences in other characteristics of the nociceptive system may yet provide insight into why some spinal pain is so highly prevalent; nociceptive distance-based summation may be highly relevant where two or more conditions co-exist in close proximity.
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Naugle KM, Cruz-Almeida Y, Fillingim RB, Staud R, Riley JL. Increased spatial dimensions of repetitive heat and cold stimuli in older women. Pain 2017; 158:973-979. [PMID: 27598411 DOI: 10.1097/j.pain.0000000000000709] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Protocols of temporal summation (TS) of pain typically involve the delivery of brief repetitive noxious pulses of a constant intensity while measuring the perceived intensity of pain after each pulse. The size percept of noxious repetitive stimulation has been poorly characterized. Furthermore, no studies have investigated age differences in TS of cold pain. The current study examined TS of pain intensity and the perceived size of the painful area during repetitive noxious heat and cold pulses in healthy younger (n = 104) and older adults (n = 40). Trials of 10 brief repetitive noxious heat or cold pulses were delivered to the upper extremities. Participants rated the perceived size of the painful area or intensity of pain after each pulse. The magnitude of change for the size percept and intensity for pain were calculated for each trial. The results indicated that older adults experienced greater TS of the size percept of cold stimuli compared with younger adults. Additionally, older women experienced greater TS of the size percept of heat stimuli compared with older men and all younger participants. No overall age or sex differences were found in the TS of pain intensity for cold or heat trials. These results suggest dysfunctional modulation of the spatial percept of the painful stimuli by older adults, and in particular older women, during repetitive noxious thermal pulses.
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Affiliation(s)
- Kelly M Naugle
- Department of Kinesiology, School of Physical Education and Tourism Management, Indiana University Purdue University Indianapolis, IN, USA
| | - Yenisel Cruz-Almeida
- College of Medicine and Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA
| | - Roger B Fillingim
- College of Dentistry and Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA
| | - Roland Staud
- College of Medicine and Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA
| | - Joseph L Riley
- College of Dentistry and Pain Research and Intervention Center of Excellence, University of Florida, Gainesville, FL, USA
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Pain facilitation and pain inhibition during conditioned pain modulation in fibromyalgia and in healthy controls. Pain 2017; 157:1704-1710. [PMID: 27045524 DOI: 10.1097/j.pain.0000000000000573] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Although fibromyalgia (FM) is associated with a deficit in inhibitory conditioned pain modulation (CPM), the discriminative power of CPM procedures is unknown. Moreover, the high intersubject heterogeneity in CPM responses in FM raises the possibility that a sizeable subgroup of these patients may experience pain facilitation during CPM, but the phenomenon has not been explicitly studied. To address these issues, 96 patients with FM and 71 healthy controls were recruited. Thermal stimuli were used to measure pain thresholds. Pain inhibition was elicited using a tonic thermal test (Peltier thermode) administered before and after activation of CPM mechanisms using a cold pressor test. Thermal pain thresholds were lower in patients with FM than in healthy controls. Pain ratings during the cold pressor test were higher in patients with FM, relative to controls. The CPM inhibitory efficacy was lower in patients with FM than in controls. The CPM procedure had good specificity (78.9%) but low sensitivity (45.7%), whereas a composite pain index had good sensitivity (75.0%) and specificity (78.9%). Finally, the rate of patients with FM who reported pain facilitation during the CPM procedure was found to be significantly increased compared with that of controls (41.7% vs 21.2%). The good discriminative power of the composite pain index highlights the need for further validation studies using mechanistically relevant psychophysical procedures in FM. The low sensitivity of the CPM procedure, combined with the large proportion of patients with FM experiencing pain facilitation during CPM, strongly suggests that endogenous pain inhibition mechanisms are deeply impaired in patients with FM, but only in a subgroup of them.
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Naugle KM, Cruz-Almeida Y, Fillingim RB, Staud R, Riley JL. Novel method for assessing age-related differences in the temporal summation of pain. J Pain Res 2016; 9:195-205. [PMID: 27114716 PMCID: PMC4833362 DOI: 10.2147/jpr.s102379] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Temporal summation (TS) of pain protocols typically involve the delivery of brief repetitive noxious stimuli held at a constant intensity and measuring the consequent increase in the perceived intensity of pain sensations. To date, no studies have examined the effect of a TS protocol on the perceived spatial dimensions of the pain experience and its interaction with age. This study used a new TS protocol that examined changes in the perceived size of the painful area in 22 younger adults and 20 older adults. Four trials of ten brief heat pulses delivered at a constant intensity were administered on the volar forearm. Interpulse intervals (IPIs) were 2.5 seconds or 3.5 seconds. Subjects rated the peak pain intensity (trials 1 and 3) or the size of the painful area (trials 2 and 4) after each pulse on a 0-100 scale. The magnitude of summation was calculated for each trial. Three seconds and 6 seconds after delivering the last heat pulse, the subjects rated the intensity or the size of any remaining pain (aftersensations). The results indicated that older adults compared to younger adults exhibited significantly greater summation of size ratings for the 2.5-second and 3.5-second IPI trials and size of pain aftersensations at 3 seconds following the 2.5-second IPI TS trial. These results suggest that aging is associated with enhanced endogenous facilitation of the perceived size of pain. The potential clinical and mechanistic implications of enhanced TS of size of pain remain unknown and warrant further investigation.
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Affiliation(s)
- Kelly M Naugle
- Department of Kinesiology, School of Physical Education and Tourism Management, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Yenisel Cruz-Almeida
- Pain Research and Intervention Center of Excellence, University of Florida, USA; Department of Aging and Geriatric Research, College of Medicine, USA
| | - Roger B Fillingim
- Pain Research and Intervention Center of Excellence, University of Florida, USA; Department of Community Dentistry and Behavioral Science, USA
| | - Roland Staud
- Pain Research and Intervention Center of Excellence, University of Florida, USA; Department of Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
| | - Joseph L Riley
- Pain Research and Intervention Center of Excellence, University of Florida, USA; Department of Community Dentistry and Behavioral Science, USA
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Mindfulness Meditation-Based Pain Relief Employs Different Neural Mechanisms Than Placebo and Sham Mindfulness Meditation-Induced Analgesia. J Neurosci 2016; 35:15307-25. [PMID: 26586819 DOI: 10.1523/jneurosci.2542-15.2015] [Citation(s) in RCA: 196] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
UNLABELLED Mindfulness meditation reduces pain in experimental and clinical settings. However, it remains unknown whether mindfulness meditation engages pain-relieving mechanisms other than those associated with the placebo effect (e.g., conditioning, psychosocial context, beliefs). To determine whether the analgesic mechanisms of mindfulness meditation are different from placebo, we randomly assigned 75 healthy, human volunteers to 4 d of the following: (1) mindfulness meditation, (2) placebo conditioning, (3) sham mindfulness meditation, or (4) book-listening control intervention. We assessed intervention efficacy using psychophysical evaluation of experimental pain and functional neuroimaging. Importantly, all cognitive manipulations (i.e., mindfulness meditation, placebo conditioning, sham mindfulness meditation) significantly attenuated pain intensity and unpleasantness ratings when compared to rest and the control condition (p < 0.05). Mindfulness meditation reduced pain intensity (p = 0.032) and pain unpleasantness (p < 0.001) ratings more than placebo analgesia. Mindfulness meditation also reduced pain intensity (p = 0.030) and pain unpleasantness (p = 0.043) ratings more than sham mindfulness meditation. Mindfulness-meditation-related pain relief was associated with greater activation in brain regions associated with the cognitive modulation of pain, including the orbitofrontal, subgenual anterior cingulate, and anterior insular cortex. In contrast, placebo analgesia was associated with activation of the dorsolateral prefrontal cortex and deactivation of sensory processing regions (secondary somatosensory cortex). Sham mindfulness meditation-induced analgesia was not correlated with significant neural activity, but rather by greater reductions in respiration rate. This study is the first to demonstrate that mindfulness-related pain relief is mechanistically distinct from placebo analgesia. The elucidation of this distinction confirms the existence of multiple, cognitively driven, supraspinal mechanisms for pain modulation. SIGNIFICANCE STATEMENT Recent findings have demonstrated that mindfulness meditation significantly reduces pain. Given that the "gold standard" for evaluating the efficacy of behavioral interventions is based on appropriate placebo comparisons, it is imperative that we establish whether there is an effect supporting meditation-related pain relief above and beyond the effects of placebo. Here, we provide novel evidence demonstrating that mindfulness meditation produces greater pain relief and employs distinct neural mechanisms than placebo cream and sham mindfulness meditation. Specifically, mindfulness meditation-induced pain relief activated higher-order brain regions, including the orbitofrontal and cingulate cortices. In contrast, placebo analgesia was associated with decreased pain-related brain activation. These findings demonstrate that mindfulness meditation reduces pain through unique mechanisms and may foster greater acceptance of meditation as an adjunct pain therapy.
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Inter-individual differences in pain processing investigated by functional magnetic resonance imaging of the brainstem and spinal cord. Neuroscience 2015; 307:231-41. [DOI: 10.1016/j.neuroscience.2015.08.059] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 08/23/2015] [Accepted: 08/24/2015] [Indexed: 01/01/2023]
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Exogenously induced brain activation regulates neuronal activity by top-down modulation: conceptualized model for electrical brain stimulation. Exp Brain Res 2015; 233:1377-89. [DOI: 10.1007/s00221-015-4212-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 01/22/2015] [Indexed: 12/23/2022]
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Spatial Summation of Pain in Humans Investigated Using Transcutaneous Electrical Stimulation. THE JOURNAL OF PAIN 2015; 16:11-8. [DOI: 10.1016/j.jpain.2014.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 09/24/2014] [Accepted: 10/08/2014] [Indexed: 01/02/2023]
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Raz N, Granovsky Y, Defrin R. Investigating the neural processing of spatial summation of pain: the role of A-delta nociceptors. Exp Brain Res 2014; 233:405-13. [DOI: 10.1007/s00221-014-4123-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 10/04/2014] [Indexed: 11/24/2022]
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Tremblay F. On the issue of inter-correlation in proprioceptive ability across body areas: a comment on Han, et al. (2013). Percept Mot Skills 2014; 117:597-600. [PMID: 24611259 DOI: 10.2466/24.10.23.pms.117x27z5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In this comment, a critical point of view is presented regarding a recent report by Han, et al. (2013), where the authors asked whether proprioceptive acuity in a given joint is correlated with that in another joint. The criticism is first directed at the rationale of the study to address the problem of establishing parallels between physiological processes involved in muscle force production and pain and those involved in proprioception. Then, some issues are indicated with regard to the methodology used in the report to assess proprioceptive acuity at different joints.
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Cruz-Almeida Y, Fillingim RB. Can quantitative sensory testing move us closer to mechanism-based pain management? PAIN MEDICINE (MALDEN, MASS.) 2014; 15:61-72. [PMID: 24010588 PMCID: PMC3947088 DOI: 10.1111/pme.12230] [Citation(s) in RCA: 193] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE This review summarizes the scientific literature relating to the use of quantitative sensory testing (QST) for mechanism-based pain management. DESIGN A literature search was undertaken using PubMed and search terms including quantitative sensory testing, pain, chronic pain, response to treatment, outcome measure. SETTINGS AND PATIENTS Studies including QST in healthy individuals and those with painful disorders were reviewed. MEASURES Publications reported on QST methodological issues including associations among measures and reliability. We also included publications on the use of QST measures in case-control studies, their associations with biopsychosocial mechanisms, QST measures predicting clinical pain, as well as predicting and reflecting treatment responses. RESULTS Although evidence suggests that QST may be useful in a mechanism-based classification of pain, there are gaps in our current understanding that need to be addressed including making QST more applicable in clinical settings. There is a need for developing shorter QST protocols that are clinically predictive of various pain subtypes and treatment responses without requiring expensive equipment. Future studies are needed, examining the clinical predictive value of QST including sensitivity and specificity for pain classification or outcome prediction. These findings could enable third-party payers' reimbursement, which would facilitate clinical implementation of QST. CONCLUSIONS With some developments, QST could become a cost-effective and clinically useful component of pain assessment and diagnosis, which can further our progress toward the goal of mechanism-based personalized pain management.
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Affiliation(s)
- Yenisel Cruz-Almeida
- Pain Research and Intervention Center of Excellence, Department of Community Dentistry & Behavioral Science, University of Florida, Gainesville, Florida, USA
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Price DD. Dorsal horn neuronal responses and quantitative sensory testing help explain normal and abnormal pain. Pain 2013; 154:1161-1162. [DOI: 10.1016/j.pain.2013.04.045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 04/30/2013] [Indexed: 10/26/2022]
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Sikandar S, Ronga I, Iannetti GD, Dickenson AH. Neural coding of nociceptive stimuli—from rat spinal neurones to human perception. Pain 2013; 154:1263-73. [DOI: 10.1016/j.pain.2013.03.041] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 03/21/2013] [Accepted: 03/29/2013] [Indexed: 11/26/2022]
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Coghill RC. Individual differences in the subjective experience of pain: new insights into mechanisms and models. Headache 2013; 50:1531-5. [PMID: 20958300 DOI: 10.1111/j.1526-4610.2010.01763.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Individual differences in pain sensitivity have long remained a perplexing and challenging clinical problem. How can one individual have a sensory experience that is vastly different than that of another, even when they have received similar sensory input? Developing an understanding of such differences and the mechanisms that support them has progressed substantially as psychophysical findings are integrated with measures of brain activation provided by functional brain imaging techniques. Continued delineation of these mechanisms will contribute substantially to the development of combined psychophysical/psychological models that can be used to optimize pain treatment on an individual-by-individual basis.
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Affiliation(s)
- Robert C Coghill
- Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, NC, USA
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Vierck CJ, Whitsel BL, Favorov OV, Brown AW, Tommerdahl M. Role of primary somatosensory cortex in the coding of pain. Pain 2013; 154:334-344. [PMID: 23245864 PMCID: PMC4501501 DOI: 10.1016/j.pain.2012.10.021] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 09/15/2012] [Accepted: 10/29/2012] [Indexed: 02/04/2023]
Abstract
The intensity and submodality of pain are widely attributed to stimulus encoding by peripheral and subcortical spinal/trigeminal portions of the somatosensory nervous system. Consistent with this interpretation are studies of surgically anesthetized animals, demonstrating that relationships between nociceptive stimulation and activation of neurons are similar at subcortical levels of somatosensory projection and within the primary somatosensory cortex (in cytoarchitectural areas 3b and 1 of somatosensory cortex, SI). Such findings have led to characterizations of SI as a network that preserves, rather than transforms, the excitatory drive it receives from subcortical levels. Inconsistent with this perspective are images and neurophysiological recordings of SI neurons in lightly anesthetized primates. These studies demonstrate that an extreme anterior position within SI (area 3a) receives input originating predominantly from unmyelinated nociceptors, distinguishing it from posterior SI (areas 3b and 1), long recognized as receiving input predominantly from myelinated afferents, including nociceptors. Of particular importance, interactions between these subregions during maintained nociceptive stimulation are accompanied by an altered SI response to myelinated and unmyelinated nociceptors. A revised view of pain coding within SI cortex is discussed, and potentially significant clinical implications are emphasized.
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Affiliation(s)
- Charles J Vierck
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, FL 32610-0244, USA Department of Physiology, University of North Carolina School of Medicine, Chapel Hill, NC, USA Department of Computer Sciences, University of North Carolina School of Medicine, Chapel Hill, NC, USA Senior School, Shadyside Academy, Pittsburgh, PA, USA
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Weissman-Fogel I, Brayer-Zwi N, Defrin R. Spatial resolution of the pain system: a proximal-to-distal gradient of sensitivity revealed with psychophysical testing. Exp Brain Res 2011; 216:181-90. [DOI: 10.1007/s00221-011-2924-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 10/20/2011] [Indexed: 12/31/2022]
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The interactions between spatial summation and DNIC: Effect of the distance between two painful stimuli and attentional factors on pain perception. Pain 2010; 151:489-495. [DOI: 10.1016/j.pain.2010.08.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 07/08/2010] [Accepted: 08/06/2010] [Indexed: 11/17/2022]
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